Apparatus for wrapping stacked compressible materials in a thermo-shrinkable plastics film

ABSTRACT

An apparatus for wrapping stacked compressible materials in thermo-shrinkable plastics film and capable of operating in a continuous sequence on consecutive stacks. The apparatus having a wrapping, a heating and a cooling station provided respectively, with lower first, second and third consecutively aligned roller conveyers, which are at the same level and are driven independently at desired times to convey a stack into and out of each station in turn and halting the stack in each station for a desired period. Each station is provided with an upper press member having an upper conveyer mounted on its underside driven in synchronism with the corresponding lower conveyer. The upper conveyers at the heating and cooling stations are maintained at the same level as the upper conveyer at the wrapping station so that the compression of the stack achieved at the wrapping station is maintained at the other two stations during the film shrinking process.

Lucas 1 Oct. 15, 1974 1 1 APPARATUS FOR WRAPPING STACKIED COMPRESSHBLEMATERIALS W A TiiiERMO-SHRTNKABLE PLASTDCS FlLM [76] Inventor: JeanLouis Lucas, avenue de la [30] Foreign Application Priority Data [56]References Cited UNITED STATES PATENTS 2,561,069 7/1951 Peterson 198/1622,841,270 7/1958 Bombard 198/165 3,156,812 11/1964 Forman et a1, 34/2253,309,835 3/1967 Peppler ...,34/225 3,402,475 9/1968 Johansen et a1.34/236 3,430,358 4/1969 Denker 34/225 3,660,962 5/1972 Bliss et a1 53/303,711,961 1/1973 Spiegel et a1, 34/232 Mclgnurd 34/66 Kongcr 53/184Primary Examiner-William F. ODea Assistant ExaminerPaul DevinskyAttorney, Agent, or Firm-Arthur B. Colvin 5 7 ABSTRACT An apparatus forwrapping stacked compressible materials in thermo-shrinkable plasticsfilm and capable of operating in a continuous sequence on consecutivestacks. The apparatus having a wrapping, a heating and a cooling stationprovided respectively, with lower first, second and third consecutivelyaligned roller conveyers, which are at the same level and are drivenindependently at desired times to convey a stack into and out of eachstation in turn and halting the stack in each station for a desiredperiod. Each station is provided with an upper press member having anupper conveyer mounted on its underside driven in synchronism with thecorresponding lower conveyer. The upper conveyers at the heating andcooling stations are maintained at the same level as the upper conveyerat the wrapping station so that the compression of the stack achieved atthe wrapping station is main tained'at the other two stations during thefilm shrinking process.

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APPARATUS FOR WRAPPING STAtIKED COMPRESSIBLE MATERIALS llN ATHERMU-SHRINKABLE PLASTllCS FllLM The present invention relates to anapparatus operating in a continuous sequence for wrapping stackedcompressible materials in a thermo-shrinkable plastics film.

It is known that thermo-shrinkable plastics materials are available inthe form of films facilitating an automatic and rational operation forwrapping products supplied for sale, the advantages of which are, interalia, a saving in the cost of the materials used, a reduction in thelabor cost, a visible presentation of the product, storage andtransportation out of doors without any fear of the action of ambienthumidity. This method of wrapping has been decided on for compact andnon-deformable products, of any shape, by means of appropriatethermo-shrinkable plastics films. As regards compressible materials, ormaterials subject to the phenomenon of expansion when moist, such aspaper, cardboard, paper or cardboard folded boxes, fibres, textiles,corrugated cardboard or any product able to be stacked, with or withouta palette, the solution of the packaging problem required a preliminaryoperation of pressing said product, then keeping it at a reduced volumeduring the shrinkage of the cover as well as during its cooling.

Current techniques offer apparatuses characterised by the arrival ofproducts which have not been pressed, already wrapped in their cover,along a feed path having freely rotating or motorized rollers, whichguide them to a press plate. Said press is mounted on a carriage alsoprovided with freely rotating or motorized rollers, which is able tomove the press arrangement and pressed products along an axisperpendicular to the axis of translation of the roller path. At the endof the operation, the press and the products are introduced into aheating oven. After a predetermined period of time, the oven is openedand the carriage leaves the oven to allow the cover to cool. The lastoperation is that of raising the press plate for discharging theproducts onto the discharge roller path in order to obtain the desiredresult, namely: products which are perfectly wrapped by a cover which isin close contact therewith.

A first drawback of this apparatus resides in the fact that the variousoperations of pressing, heating and cooling are effected inperpendicular directions.

In fact, the-press and products are brought into the heating oven bymeans of a second roller'path perpendicular to the former. Due to this,after passing into the heating oven, the press and products are oncemore displaced on the second roller path and kept on one of the rollerpaths for the time necessary for cooling, the press only being releasedafter complete cooling of the plastics envelope. A new cycle of placingthe load under pressure and moving it into the heating oven may onlytake place when said press has been released.

There is thus a considerable period of time during which the press andother members such as the heating oven are inoperative, which does notfacilitate continuous packing of the loads to be wrapped.

Moreover, the fact of introducing the press into the 6s heating ovenforces the designer to provide an oven of considerable volume tofacilitate the introduction of the different presses whose heights vary.

Another drawback resides in the fact that said press is also partlysubjected to the temperature prevailing inside said oven, which maydamage the sensitive parts of the press.

Another drawback in apparatuses existing hitherto and in thenon-automatic sequence of operations; is to place the product on apalette on roller paths located upstream and downstream and on the presscarriage, the latter being provided with freely rotating rollersrequiring the operator to undertake manual operations, the times of thevarious operations being left to the personal initiative of saidoperator; the rhythm and reliability of packing leaving much to bedesired. Finally, the location of the electric control unit controllingthe pressing, heating, opening and closing of the oven doors, requiresthe operator to move about a great deal or makes a second operatornecessary.

It is the object of the present invention to remedy the aforesaiddrawbacks and to propose an apparatus capable of producing continuouswrapping of compressible products in a therrno-shrinkable plastics film,said apparatus being of the type comprising a station for prewrapping inthe plastics film and for placing the compressible materials to bewrapped under pressure at the desired value, an oven for heating theplastics envelope covering said materials to be wrapped and a coolingstation in which the heated envelope is cooled to allow shrinkage ofsaid envelope in order that it follows the shape of the pressedmaterials perfectly, characterised in that the various stations forpre-wrapping, heating and coolingare located in a line and in that themeans for placing the materials under pressure are incorporated in theheating oven.

Owing to this, the various stages of pre-wrapping the materials, heatingthe thermo-shrinkable wrapping film and cooling said plastics film maybe carried out continuously. Thus,'whilst heating the envelope of astack of materials, itis possible to pre-wrap the next stack whichpasses intothe heating oven after the discharge of the preceding stackwhich is discharged into the cooling station where it is cooled duringthe heating of the stack admitted to the heating oven.

According to another feature of the invention, the heating oven isvariable in height and is constituted by two half-shells open at one oftheir sides and movable in an air tight manner with respect to eachother.

Due to this, the height of the heating oven is adapted to the height ofthe stack of materials which makes it possible to limit the productionof hot air to the volume of the heating oven,

According to another feature, the stations for prewrapping, heating andcooling are constituted by rollers for conveying and supporting thematerials to be wrapped, the rollers of each station being able to berotated in synchronism with the rollers of another operating stationsuch that the materials are displaced in a uniform manner and smoothlywhen passing from one working stationto another. Due to the alignment ofsaid rollers in the same horizontal plane, the materials are alwayspressed at the same value.

Further features and advantages will become apparent on reading theensuing description given as a nonlimiting example and with reference tothe accompanying drawings in which:

FIG. 11 is an elevational view of the wrapping apparatus according toone embodiment of the invention;

FIG. 2 is a plan view of the heating station.

FIG. 3 is a sectional view of the heating oven.

According to the embodiment illustrated in FIGS. 1 to 3, the apparatusis constituted by different working stations located in a line,connected to each other by sections of roller path constituting a singleroller and support path whose various parts and functions will bedescribed hereafter.

Station 1 comprising conveying rollers 6 rotated or not rotated isintended to receive a handling palette 9 on which is placed a stack ofcompressible materials 8. In this station 1 the stack 8 is wrapped by anevelop ll) of thermo-shrinkable plastics material known per se. Thestack 8 covered by its envelope 10 without special precautions isbrought into a station 2 for putting it under pressure, the conveyingand support rollers 6a of which are firstly at the same level as therollers 6 and secondly rotated by means of a reduction motor 7 and otherparts known per se. Located in thisvstation 2 is a press provided with astand 11 and bracket 12, said press being able to displace along theroller path,'i.e., perpendicularly to the generatrices of the conveyorand support rollers 6a; provided on the lower face of the pressure plateare conveyor rollers 16 rotated by reduction motors 17, the upperrollers 16 and lower rollers 6a being driven in synchronism in mannerknown per se. The pressure plate 15 and rollers 16 being brought intocontact with the top of the stack 8 covered with its envelope 10, theirdescent is controlled by means of a hydraulic cylinder device 13controlled by a central station 14 so as to apply to said covered stackthe desired pressure depending on the nature of the material to bewrapped and which, in the case of corrugated card or folding boxes is ofthe order of lT/m While the stack 8 is being placed under pressure, theenvelope 10 is put in position so that the latter appropriately coversthe materials displacing said envelope if necessary and, this is inorder that at the time of the subsequent shrinkage of the plasticsmaterial, there are no parts of least resistance and parts where saidenvelope is not applied uniformly against the materials.

When the stack 8 has been placed under pressure, the latter is suppliedby means of rollers 16 and 6a to a heating station 3 in which isprovided a heating oven 19 provided with two doors 2t) and 20a slidingin the direction of the generatrices of the rollers of the roller path.The oven 19 is constituted by at least two halfshells 30 and 31, in theshape of a U and able to be displaced with respect to each other inorder to produce with the doors 20 and 20a, a vessel which is closed inan air tight manner by seals 32. Provided in the bases of thehalf-shells 30 and 31 are conveyor rollers Ma and 6b rotated byreduction motors l7 and 7 such that they rotate in synchronism with eachother and with the rollers 16 and 6a of the pressure station 2. In thismanner, the stack 8 passes from station 2 to station 3 continuously andsmoothly. In addition, since the rollers 16a are strictly at the samelevel as the rollers 16 and since the pressure able to push the upperhalf-shell 30 onto said stack 8 is also equal to that exerted by therollers 16 in the station 2, said stack is transferred from station 2 tostation 3 under the same pressure. In this way, there is no tendency forthe stack to expand between stations 2 and 3 and the heating of theplastics envelope 10 may be carried out appropriately, the stack 8always being at the height that it must have after cooling.

Preferably, the rollers 16a are made of special plastics material whichis resistant to heat or covered by an endless belt 18 made of afireproof and strong material, for example a metal belt covered with afilm of material known by the trade name TEFLON. Similarly, said beltmay be made of asbestos. This makes it possible to avoid direct contactbetween the rollers and the hot thermo-shrinkable envelope, whichcontact could cause adhesion and consequently tearing of the envelope.Moreover, this also makes it possible that the contact surface appliedto said envelope is plane which gives the stack when cooled perfectlyplane surfaces, at least, as regards the upper and lateral faces.Naturally, the lower rollers 6a may be protected in the same manner asthe rollers 16a, which would give the stack arrangement perfectly planewalls.

In a preferred embodiment of the invention, the rollers 16a provided ornot with their belt, are secured to the end wall of an internal sleeve27, in the shape of an inverted U and housed inside the upper half-shell30.

The sleeve 27 partially surrounds the stack 8 and provides between itsouter wall and the inner wall of said half-shell 30, an annular space 28in which circulates hot pulses of air 23, provided with its burner 24and blower 25. The hot air is channelled towards the stack 8 by means ofan aperture 33 defined by the lower edge of the sleeve 27 and the lowercurved edge 30a of the half-shell 30. The rollers 16a and the sleeve aredis placed with respect to the stack 8 by any appropriate means such asa press similar to that provided in station 2. In this case, the sleeve27 and the rollers 16a are integral with the press plate, thedisplacement of said press plate being effected along a stand and bymeans of a cylinder device associated with a hydraulic central station.

In order to improve the heating qualities and to reliably avoid the riskof adhesion of the pressure rollers 16a to the plastics envelope 10, theupper part of the oven and said rollers 1611 may be cooled by means ofan appropriate cooling circuit known per se and which has not been shownin order not to over burden the drawing.

After heating the plastics envelope in the heating oven, the rollers 16aand 6b are set in rotation, which causes the discharge of the stack 3from said heating oven and towards a cooling station 4 in which islocated a press similar to those described previously, the upper rollers16b integral with the pressure plate and the lower rollers 6 of theroller path being rotated in synchronism with each other and with therollers 16a and 6b, the rollers 16b and 6c being strictly at the samelevel as the rollers 16a and 6b respectively. The stack 8 always kept atthe same pressure is displaced along the roller path from station 4until the plastics envelope It) is completely cooled, said coolingcausing, in manner known per se, the shrinkage of said plasticsenvelope, which is thus applied against the entire surface of thematerials such that the latter are appropriately wrapped and without anypossiblity of resuming their position before being placed underpressure, the wrapped materials being in the form illustrated in FIG. 1in the discharge station 5 which is adjacent the station 4 and providedwith rollers 6d which are driven or not driven and located at the samelevel as the rollers 60.

Naturally, the various operations such as pressing, heating anddischarge are controlled by an electric circuit not illustrated and notpart of the invention. in fact, the apparatus according to the inventionis associ-- ated with a central electronic control means which sets thevarious conveying rollers in rotation and which controls the opening ofthe doors 2% and Na in the position illustrated in broken line in FIG.3. Thus, while a stack ii is being discharged from the heating oven l9,i.e., as soon as the stack ii is displaced by the roilers res, anotherstaclt may be displaced by the rollers res to bring it into the heatingoven l9 when said staclrs have the same height.

in the case where the next stack to be heated is of a different heightto that which is to be discharged from said heating oven, the centralelectronic control means only authorises the transfer from station 2 tostation 3 when the stack being discharged is completely outside theheating oven W, Le, when it is in the cooling sta tion 4. Moreover, whenthe height of a pressed stack is determined, the central electroniccontrol means defines the position of the various rollers 1 6a and Mbsuch that the stack is transferred from one station to the other withoutthe pressure applied thereto varying in any manner whatever.

Thus, the stoppages and starting up of the reduction motors 7 and 17 aswell as the sending of hot air into the oven is programmed depending onthe nature of the material to be wrapped. in the same manner, the timeduring which the plastics envelope is exposed inside the heating oven isvariable. This is the reason why this variation is also programmed andcontrolled by the central electronic control means. We can thus eee theprogress made by the apparatus according to the invention, since thewrapping of stacks of any height may be undertaken continuously, saidapparatus being capable of wrapping, in a given time, three times morethan was possible with lcnown apparatuses.

Naturally, the present invention is not limited to the embodimentsdescribed, but on the contrary extends to all variations. Thus, station2 may be eliminated if the heating oven comprises members forpositioning the envelope, which are able to be controlled from outsidesaid heating oven. in fact, the station 2 for placing the stack underpressure is dispensible only if the heating oven is equipped with suchmembers. if these members exist, the stack previously covered with itsenvelope may be sent directly into the heating oven, inside whichparatus comprising, in combination, a horizontal antifriction conveyormeans for supporting for advancement along a linear path, a palletcarrying an article to be wrapped, said article being covered by ashrinkable plastic film, a compression zone at an upstream positionalong said path, said zone including a planar pressure plate means inparallel spaced relation to said conveyor means and shiftable toward andaway therefrom for squeezing said article between said plate means andconveyor means, drive means on said pressure plate means for engagingthe film portion above the upper surface of said article and advancingsaid compressed article along said path, a heating zone adjacent anddownstream of said compression zone positioned to receive articlescompressed at said compression zone, said heating zone including asecond compression plate means in parallel spaced relation to saidconveyor and shiftable toward and away from said conveyor, said sec ondplate means including second drive means for en gaging the film abovethe upper surface of said article and advancing said article in saiddirection, heating means at said heating zone for heating said film asthe same traverses said zone, and a cooling zone along said patchadjacent and in downstream relation to said heating zone, said coolingzone including a third compression plate means in parallel spacedrelation to said conveyor, said third plate means including third drivemeans for engaging said film above the upper surface of the articleemerging from said heat zone and advancing the same along said path, thespacing of said first, second and third drive means from said conveyorbeing substantially identical, whereby said article'and film aresubjected to a constant compressive force as the same traverse saidpath.

2.. Apparatus in accordance with claim ll wherein said heating zoneincludes a heat chamber, the upper surface of which is defined by saidsecond drive means, said chamber including upper and lower,telescopically interfitting, vertically relatively movable half shells,said half shells having open portions at their upstream and downstreamends to permit passage therethrough of said article and film.

3. Apparatus in accordance with claim 2 wherein said heating chamberincludes upstream and downstream door portions shiftable in a directionnormal to said path between first and second positions, respectively,forming with said ends of said half shells a substantially airimpervious enclosure, and in clearing relation of said ends.

Apparatus in accordance with claim 3 wherein said upper half shellincludes an internal sleeve resistant to heat and adapted to be disposedabout said article and film, said sleeve and upper half shell definingtherebetween an annular space for the circulation of heated air.

5. Apparatus in accordance with claim 1 wherein at least one of saiddrive means comprises a plurality of rollers mounted on a said platemeans, the lower peripheries of said rollers being in coplanaralignment, and an endless anti-friction belt arrayed about said rollersand having a lower flight engaged against said lower peripheries.

6. Apparatus in accordance with claim 5 and including means fordirecting a source of cooling fluid against

1. A continuously operating shrink film wrapping apparatus comprising,in combination, a horizontal anti-friction conveyor means for supportingfor advancement along a linear path, a pallet carrying an article to bewrapped, said article being covered by a shrinkable plastic film, acompression zone at an upstream position along said path, said zoneincluding a planar pressure plate means in parallel spaced relation tosaid conveyor means and shiftable toward and away therefrom forsqueezing said article between said plate means and conveyor means,drive means on said pressure plate means for engaging the film portionabove the upper surface of said article and advancing said compressedarticle along said path, a heating zone adjacent and downstream of saidcompression zone positioned to receive articles compressed at saidcompression zone, said heating zone including a second compression platemeans in parallel spaced relation to said conveyor and shiftable towardand away from said conveyor, said second plate means including seconddrive means for engaging the film above the upper surface of saidarticle and advancing said article in said direction, heating means atsaid heating zone for heating said film as the same traverses said zone,and a cooling zone along said patch adjacent and in downstream relationto said heating zone, said cooling zone including a third compressionplate means in parallEl spaced relation to said conveyor, said thirdplate means including third drive means for engaging said film above theupper surface of the article emerging from said heat zone and advancingthe same along said path, the spacing of said first, second and thirddrive means from said conveyor being substantially identical, wherebysaid article and film are subjected to a constant compressive force asthe same traverse said path.
 2. Apparatus in accordance with claim 1wherein said heating zone includes a heat chamber, the upper surface ofwhich is defined by said second drive means, said chamber includingupper and lower, telescopically interfitting, vertically relativelymovable half shells, said half shells having open portions at theirupstream and downstream ends to permit passage therethrough of saidarticle and film.
 3. Apparatus in accordance with claim 2 wherein saidheating chamber includes upstream and downstream door portions shiftablein a direction normal to said path between first and second positions,respectively, forming with said ends of said half shells a substantiallyair impervious enclosure, and in clearing relation of said ends. 4.Apparatus in accordance with claim 3 wherein said upper half shellincludes an internal sleeve resistant to heat and adapted to be disposedabout said article and film, said sleeve and upper half shell definingtherebetween an annular space for the circulation of heated air. 5.Apparatus in accordance with claim 1 wherein at least one of said drivemeans comprises a plurality of rollers mounted on a said plate means,the lower peripheries of said rollers being in coplanar alignment, andan endless anti-friction belt arrayed about said rollers and having alower flight engaged against said lower peripheries.
 6. Apparatus inaccordance with claim 5 and including means for directing a source ofcooling fluid against said rollers.